This invention relates to bushings, particularly to a coupling bushing for use with gear box structures and the like which are coated with corrosion resistant material for permitting use of the bushing within a corrosive environment, particularly a salt water environment.
Conventional industrial equipment employing coupling bushings are generally devised as heavy duty tools, particularly constructed to withstand long-time usage under extreme power requirements and under adverse conditions. However, it has been found that the life span for a bushing in a salt water or other harsh environment is reduced considerably from many years to only a few weeks before corrosion deteriorates the bushing beyond further useful service. The materials utilized in conventional gear boxes and bushings associated therewith by way of example are generally made of ductile iron, cast iron, powdered metal (sintered steel) or steel and, in special applications, stainless steel in order to ensure long life usage. Since ductile iron, cast iron, powdered metal and steel offer little or no protection, eventually stainless steel was substituted therefor to obviate this problem for equipment intended for use in a harsh environment. However, even stainless steel is not able to survive salt water environment, and at best, may only prolong the life of the bushing.
A corrosive environment particularly affects the operative connection between the output shaft of a gear box and its associated bushings which must be necessarily disconnected from the host shaft when a driving or driven mechanism to which the gear box is connected is disassembled. Even slight corrosion between the bushing and output shaft results in difficulty if not an impossibility to disengage their operative connection.
Therefore, it is a principal object of the present invention to enhance the life span of coupling bushings for use with gear boxes and other industrial equipment under adverse corrosive environments such as those involving salt water, fertilizers, concrete, sewage disposal, and chemical processes.
Another object of the present invention is to improve the art of coupling bushings by permitting the use of standard materials susceptible to corrosion in the construction of the same and yet extend the life span for these devices.
These and other objects of the present invention are achieved by the present invention which is directed to the application to bushing surfaces of a corrosion resistant material, particularly a coating of a fluorocarbon polymer such as a polytetrafluoroethylene polymer. When, however, a fluorocarbon polymer is applied directly to the bushing surfaces, a thermosettable binder material should also be employed to effectuate proper adherence of the coating to the metal. When plural coating layers are employed, top or overcoat layers of the polymer do not include such a binder material and adhere under a proper temperature-time exposure to the base or prime coating. Thicknesses of the coatings have been particularly adapted for this part of the assembly. The thickness is devised in accordance with acceptable tolerances associated with details of the bushing in order to avoid any binding during engagement or disengagement of the bushing from a hub shaft for the gear box and the prevention of inadvertent wear of the material from these parts, and as pointed hereinafter, coatings according to the present invention afford better seating and removal characteristics.